typedef unsigned char u8;
typedef signed char s8;
#define C1 (19595)
#define C2 (38470)
#define C3 (7471)

#define C4 (32767)
#define C5 (-15119)
#define C6 (-17648)

#define C7 (13282)
#define C8 (-32767)
#define C9 (19485)

#define CONST (1 << 15)

void foo(u8 *in, u8 *out, int n) {
    int i;
    u8 *read = in,
	 *write = out;
    u8 x1, x2, x3, y1 = 0;
    s8 y2, y3;

    for(i = 0; i < n; i++) {
        x1 = *read++;
        x2 = *read++;
        x3 = *read++;
	y1 = (u8) ((C1 * x1 + C2 * x2 + C3 * x3 + CONST) >> 16);
	y2 = (s8) ((C4 * x1 + C5 * x2 + C6 * x3 + CONST) >> 16);
	y3 = (s8) ((C7 * x1 + C8 * x2 + C9 * x3 + CONST) >> 16);

        *write++ = y1;
        *write++ = (u8) y2;
        *write++ = (u8) y3;
    }
}